This is an issue that tends to come up time and time again in the prepper world and I had the same problem until finding a man that was like minded (which believe me took a long time to find).
How do I get my partner to prep and not look at me like I am crazy?
First you have to realize that the prepper community is a small percentage of the population and most are viewed as either:
"The sky is falling type" which was the Y2Ker's. So people look at that scenario and say oh you are just getting all freaked out for something that's never going to happen.
The other is "militia". Guns, camo, and standoff's.
So with these images ingrained in their mind, you start to have that talk with your partner about prepping for SHTF scenario and they get that glazed over deer in the headlights look and they blow you off.
You are left thinking "why don't they get it"?
Here is an initial approach that will be understood and received better by a partner that is not familiar with prepping.
Every year there are a myriad of natural disasters here in the United States, tornados, floods, blizzards, hurricanes, and wild fires. Most don't think about this or just think "it won't happen to me". There is no doubt that if more people had been prepared for Katrina there would have been less loss of life.
When initially talking to your partner everyone understands preparing for natural disasters. As children in school we are taught fire and tornado drills so that mindset is already there. And a natural disaster can affect you no matter what part of the country you live in or the world for that fact. Witnessing the aftermath of Katrina and the Tsunami in Japan this sets the stage for you to approach your partner and have a discussion that is rational and practical in their mind.
A definite DON'T is talking about Op Sec, guns, and WROL scenarios especially where women are concerned. That is just too much for a newbie, keep it simple and let them ease into prepping. All you are looking for initially is them to acknowledge "yes it's good to be prepared" and not look at you like your crazy. Let them come to their own conclusions because not everyone's scenario of the future is the same.
Be supportive and make it a "couples bonding experience". I know that's not exactly a bonding experience that you’re going to find on EHarmony but I know many couples that prep and this is something they do together and enjoy it! It doesn't have to be a negative or gloom and doom experience.